/*
 * @Author: windys
 * @Description: 
 * @Date: 2021-12-13 15:21:23
 */




/**
 * @param {Function} func
 * @param {number} wait
 * @param {boolean} immediate
 * @return {*}
 */
export function debounce(func: Function, wait: any, immediate: any) {
    let timeout: any, args: any, context: any, timestamp: any, result: any

    const later = function () {
        // 据上一次触发时间间隔
        const last = +new Date() - timestamp

        // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
        if (last < wait && last > 0) {
            timeout = setTimeout(later, wait - last)
        } else {
            timeout = null
            // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
            if (!immediate) {
                result = func.apply(context, args)
                if (!timeout) context = args = null
            }
        }
    }

    return (...args: any) => {
        context = this
        timestamp = +new Date()
        const callNow = immediate && !timeout
        // 如果延时不存在，重新设定延时
        if (!timeout) timeout = setTimeout(later, wait)
        if (callNow) {
            result = func.apply(context, args)
            context = args = null
        }

        return result
    }
}
